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First time accepted submitter Joe_NoOne (48818) writes "A new theory suggests that our male ancestors evolved beefy facial features as a defense against fist fights. The bones most commonly broken in human punch-ups also gained the most strength in early hominin evolution. They are also the bones that show most divergence between males and females. From the article: 'Fossil records show that the australopiths, immediate predecessors of the human genus Homo, had strikingly robust facial structures. For many years, this extra strength was seen as an adaptation to a tough diet including nuts, seeds and grasses. But more recent findings, examining the wear pattern and carbon isotopes in australopith teeth, have cast some doubt on this "feeding hypothesis". "In fact, [the australopith] boisei, the 'nutcracker man', was probably eating fruit," said Prof David Carrier, the new theory's lead author and an evolutionary biologist at the University of Utah. Instead of diet, Prof Carrier and his co-author, physician Dr Michael Morgan, propose that violent competition demanded the development of these facial fortifications: what they call the "protective buttressing hypothesis".'"

You want to avoid delving into 'just so stories', or flattering a particular cultural quirk with the status of 'universality' ("Y'know why pink is a girl color, and chicks naturally like it? Because they, like, evolved to judge the ripeness of fruits that they were gathering! Oh, wait, you mean that the association between young girls and pink and young boys and blue is actually a century or two old? Umm, never mind...); but you can infer things about lifestyle and social interaction from archeological evidence.

Undamaged bone, bone that has experienced substantial unhealed trauma (ie. that trauma was part of whatever killed the bone's owner before any healing occurred), and bone that was damaged; but subsequently healed, all look quite different if they are in reasonably well-preserved shape.

If a fossil record is adequately detailed across time, changes in skeletal structure are also quite discernable, and isotopic analysis can help determine whether those changes were driven by dietary demands, or whether they occurred for unrelated reasons.

There is no certainty to be had, and there are pitfalls to avoid; but it's hardly a morass of nescience.

Plenty of species without hands get their rape on to a degree that makes A Clockwork Orange look like Saturday morning cartoons. Ducks, just by way of example, are so nasty that the evolution of their genital morphology is basically an arms race, with female reproductive tracts getting ever longer and more convoluted, and males developing ever more grotesque Cthulhoid horror-phalluses in an attempt to not let that stop them. ("Explosive eversion and functional
morphology of the duck penis supports sexual conflict in waterfowl genitalia" is always a good read if you suspected nature of harboring any traces of benevolence...)

The explanation I've heard for useless showy features (a la peacock) is that the ability to put resources into giant shiny feathers show that you have the ability to gather enough food to live, and have leftover energy to devote to impressing the ladies. It's not so much the particulars of what the feature is, but rather having resources (or money) to burn indicates that you're successful enough to be a good mate.